Added underscore.js version 1.5.2

underscore.js is a prerequesite for backbone.js

$ wget http://underscorejs.org/underscore-min.js
$ wget http://underscorejs.org/underscore-min.map
Downloaded backbone 1.0.0

$ wget http://backbonejs.org/backbone-min.js http://backbonejs.org/backbone-min.map